SUMMARY Inflammatory bowel disease (IBD) is one of the most prevalent GI diseases in the United States, costing ~ $1.7 billion annually in treatment. The etiology of IBD remains unknown. Although IBD outcome is clearly influenced by interactions involving the brain, gut, immune system, and the environment, the contributing biological factors remain under-characterized and have been identified as a major gap in understanding the etiology of IBD. Our proposal directly addresses this gap by elucidating biological factors, such as the components of the corticotropin-releasing factors (CRF) system, whose modulation can directly influence the gut and the brain. In addition to the physical symptoms of IBD, patients often experience stress-related mood disorders. The CRF system mediates the classic stress response via activation of the hypothalamic-pituitary-adrenal (HPA) axis. However, the cellular mechanisms by which the components of the CRF system bring about their immunomodulatory and stress-coping actions during IBD remain unknown. Our preliminary data shows that the stress receptor CRF2 is a key determinant of cellular stress responses during an inflammatory insult. Our over- arching hypothesis is that CRF and urocortins, differentially signaling through CRF1 and CRF2, govern intestinal inflammation at the molecular, cellular and organ levels in a sex-specific manner. We propose to test our hypothesis in three specific aims. In Aim 1, we will determine the sex-specific role of the CRF2 receptor in modulating aspects of GI permeability, organ mass, and immune cell function at baseline and during colitis. Our pilot data shows that the gut is ?leakier? in female than in male mice. This leakiness is abrogated in mice lacking the CRF2 receptor. By measuring vascular leak and immune cell changes by flow cytometry, we will determine whether CRF2 receptor deficiency alters immune cell recruitment or migration during colitis, locally at the site of inflammation, and in the blood and spleen. The role of kinases and their targets in manifesting sex-specific effects during IBD will be ascertained. Changes in the components of the CRF system in the brain during colitis will be correlated with changes in anxiety- and depression-like behaviors. In Aim 2, we will determine the sex-specific role of urocortins and CRF agonists in modulating aspects of GI permeability, organ mass, and immune cell function at baseline and during colitis. By using approaches defined in Aim 1, we will delineate the role of 4 different agonists for the CRF2 receptor in modulating of function of CRF2 in a sex-specific manner. In Aim 3, we will determine if heteromerization of CRF receptors (CRF1:CRF2) and/or their association with scaffold proteins and heat shock proteins results in differential trafficking and signaling by their four ligands. By making tagged versions of CRF receptors and using a combination of immunoprecipitation and mass spectrometry, we will identify ancillary proteins that interact with CRF receptors to mediate context-specific signaling and trafficking. This proposal will define sex-specific signaling pathways that can be targeted for therapeutic purposes for patients with IBD.